the power supply has no connections between terminals and have a high resistance I=0 V=

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Short Circuit

power supply terminals are joined by a connection with no resistance V=0 I=

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Conventional is positive which means

current leaves the positive terminal and enters the negative

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Current in a Metal

the current is negative electrons and so they move in the opposite direction

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Ammeter

measures current (amps) and is connected in series

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Voltmeter

measures potential difference (volts) and is connected in parallel

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Increased Potential Difference on Current

increase in curren

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Ohms Law

current is directly proportional to potential difference

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Non Ohmic

not proportional

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Increases Current on Resitance

decrease in resistance

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Why does resistance increases in metals?

-free electrons -as they collide with lattice vibrations they scatter -hotter metal more vibrations -more collisions between atoms and electrons -the current decreases -if the current has decreased then the resistance has increases

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The faster electrons move

the slower the current

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Semiconductors

have fewer free electrons

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Positive Semi Conductor

resistance increases as the temperature increases

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Negative Semi Conductor

resistance decreases as the temperature decreases

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A material with a small resistivity?

it will be a good conductor as it has a large number of free electrons